1. Field of the Invention
The present invention relates to polishing pads used for creating a smooth, ultra-flat surface on such items as glass, semiconductors, dielectric/metal composites and integrated circuits.
2. Description of Related Art
Polishing generally consists of the controlled wear of an initially rough surface to produce a smooth specular finished surface. This is commonly accomplished by rubbing a pad against the surface of the article to be polished (the workpiece) in a repetitive, regular motion while a solution containing a suspension of fine particles (the slurry) is present at the interface between the polishing pad and the workpiece.
Polishing pads are normally produced by impregnation of felt with polymer solutions using water miscible solvents such as DMF followed by coagulation with water or water solvent blends, then drying and buffing or splitting/buffing. In another process the polymer solution is coated onto a substrate followed by coagulating. This process leads to the formation of vertically oriented pores (VO pores) which serve as slurry reservoir during polishing. The impregnation/coagulating method gives material with mostly horizontally oriented fibers and the coating method results in a coating without any fiber reinforcement except the fibers present in the substrate. The only way to make polishing material with vertically oriented fibers is by laminating horizontally oriented product to make a vertically oriented product such as described in U.S. Pat. No. 4,728,552.
A patent which shows one method of forming a polishing sheet material with pores on the surface to provide slurry reservoir is U.S. Pat. No. 4,753,838. The pad surface is made of cellular polyurethane.
A polishing pad is provided which is comprised of vertically oriented hollow fibers. Such pads can be produced by electro statically flocking fibers onto a substrate. Optionally, the pad comprised of vertically oriented hollow fibers may be coated with a polymer solution to fill the voids between the fibers. The surface of pads coated with a polymer solution may be abraded or skived to remove polymer skin and open the hollow fiber ends.
A method for polishing a workpiece is provided wherein polishing pads as described above are used to planarize a workpiece by contacting the surface of the polishing pad and a surface of the workpiece while there is motion between the polishing pad and the workpiece.